Unconventional superconductivity in superconducting topological materials (Jul. 19, 2018)

  • Published: 2018-07-10

Speaker:  Chao-Xing Liu

     Physics Department, Penn State University,

     University Park, PA 16803, USA




Majorana modes can appear as low energy quasi-particle excitations at the boundary or in the bulk of topological superconductors and are regarded as the corner stone of a new type of computation architecture, called topological quantum computation. Topological superconductivity can appear in certain classes of topological materials, which possess both inverted band structures and superconductivity when there is doping. In this talk, we will describe our efforts in exploring such type of superconducting topological materials. In the first example, we will consider a superconductor/topological-insulator/superconductor sandwich hetero-structure, in which the surface of topological insulator film becomes superconducting due to the proximity effect. Under an in-plane magnetic field, we demonstrate the occurrence of topological Larkin-Ovchinnikov phase with finite momentum pairing in this system. As a result of non-trivial topology, a chain of Majorana modes can be realized at the boundary and can be probed by STM measurement. In the second example, we will discuss a class of half-Heusler materials, which possess both inverted band structure and intrinsic superconductivity. A unique feature is that the electrons carry “effective spin” 3/2 for this class of materials. As a consequence, we demonstrate a new type of mixed pairing state, namely the mixture of s-wave singlet and d-wave quintet pairing, for such superconducting materials. Furthermore, we find topological nodal-line phases as a result of such singlet-quintet mixing, which is consistent with recent experimental observations of power law dependence of London penetration depth in these materials. These unconventional superconducting phases found in this talk will not only give a new understanding of the recent experiments in these materials, but also provide a new platform to explore topological quantum computations.



[1] Singlet-Quintet Mixing in Spin-Orbit Coupled Superconductors with j=3/2 Fermions, Jiabin Yu, Chao-Xing Liu, arXiv:1801.00083 (2018)
[2] Topological Larkin-Ovchinnikov phase and Majorana zero mode chain in bilayer superconducting topological insulator films, Lun-Hui Hu, Chao-Xing Liu, Fu-Chun Zhang, arXiv:1708.00600 (2017)
[3] Unconventional superconductivity and surface pairing symmetry in half-Heusler compounds, Qing-Ze Wang, Jiabin Yu, and Chao-Xing Liu, Phys. Rev. B 97, 224507 (2018)



Time & Date: 10:30am, July 19 (Thur.), 2018

Venue: Rm. N306, Kavli ITS [View Map]